Voltage measuring system



I Oct. 18, 1938. H, SCHUCHMANN 2,133,670

VOLTAGE MEASURING SYSTEM Filed Nov. 8, 1955 phases/fier /VVE Nro l? f/A M5 5c 40C HMA/ff ATTO/WYE r,

Patented Oct. 18, 1938 STATES PATENT oFrloE f 2,133,670 y voL'rAGE MEASURING SYSTEM Hans Schuchmann, Berlin-Schmargendorf, Germany, assignor to Siemens Apparate und Maschinen Gesellschaft mit beschrnkter Haftung, Berlin, Germany, a corporation of Germany Application November 8, 1935, Serial No. 48,843 In Germany November 8, 1934 3 Claims.

voltage of a condenser which is charged and discharged through a resistance during the time interval to be determined. As a rule and preferably also according to the invention the charging or the discharging of the condenser during the time interval to be measured is based upon a predetermined value of the voltage, so that the voltage of the condenser at the end of the time interval to be determined is a measure of the magnitude of the time interval which has been determined and need only, therefore, be accurately indicated. In most 'cases and particularly by the use of a mcrochronometer employed in connection with echo depth Sounders, it is desirable to indicate the value of the voltage attained at the end of the time interval to be determined for a relatively considerable time..(some seconds); This is, of course, only possible with the aid of a voltmeter which does not consume current. In this case particularly tube voltmeters are, therefore, employed, which, however, owing to the variety of the tube characteristics, present difculties when a damaged tube must be replaced by another.

The object of the present invention is to provide a microchronometer particularly for echo depth Sounders, whereby the above dimculties are eliminated. `'I'his object may be accomplished by designing the valve amplifying connection employed for measuring the voltage of the condenser as an alternating current amplifying connection and providing between the amplier and the measuring condenser, means, for instance, in the form of a mechanical interrupter by means of which the direct-current voltage of the condenser is converted into a periodically varying current voltage with respect to the amplifying tube.

In the accompanying drawing Fig. 1 shows an embodiment of my-invention in diagrammatic form, and Fig. 2 is a graph of certain curves referred to hereinafter.

Referring to Fig. 1, I denotes the condenser used for the measurement. By the direct-current source 2 of' constant voltage, thercondenser is charged throughout the resistance 3 and the throw-over switch 4 during the time interval to be measured. At the end of the time interval to be determined the switch 4 is thrown over into the position shown, thereby connecting the condenser I to the grid circuit of the amplifying tube 5. A negative biasing potential of the battery 6 yis impressed on the grid circuit. 1 denotes the permanent magnet f a mechanical interrupter whose contact blade 8 carries an exciting winding 9 which is fed by an alternating-current source I0. The frequency of the alternating current is such that the contact blade 8 oscillates at about 25 cycles per second. The armature 8"of the interrupter is caused to vibrate by the interaction of magnet 'I and coil 9 which receives current from the alternating current source l0, so that the armature vibrates in accordance with the frequency of.r said current. The grid is alternately connected at the frequency of the exciting alternating current to the negative biasing potential of the battery 6, and in series with the battery 6 and the condenser I.

The tube 5 is biased by a high negative potential of such magnitude that the grid will remain negative with respect to the filament even at the highest voltage which may be applied to the grid, consequently the voltage applied to the grid of the tube 5 behaves according to the line sg shown in the diagram of Fig. 2, in which the characteristic of the tube is also represented and designted by K. The variable (intermittent or fluctuating) character of the anode current is represented by the siz-zag line ia which corresponds substantially to an alternating current such as shown in dash lines in Fig. 2. The variable current might be directly supplied to an alternating-current measuring instrument. With respect to the line sg, the time t is indicated as ordinates and the voltage as v abscissae; the reverse arrangement, however, has

plied to a. direct-current measuring instrument of the moving coil type. To this end, the primary coil of the transformer II is connected to the anode ciurent circuit through a condenser I8. An exciting winding I3 surrounding the contact blade I2 of a mechanical rectifier is fed by the secondary winding of the transformer II. I4 denotes the permanent magnet of the rectier. The operation of the rectier is similar to that of interrupter 1, 8 and9, but with respect to the rectier the current for coil I3 is supplied by the amplifier 5, the frequency of which current is determined by that of source l0. A direct-current measuring instrument I5 is connected in a.

two-way connection to the secondary Winding or the transformer. An adjustable shunt resistance iti is connected in parallely relation to the measuring instrument l5. The mechanical rectier i2, i3, M5 is thus operated synchronously with the interrupter 7, 8, 9.

In the present embodiment, as illustrated in Fig. l, the interrupter and rectifier comprise two separate instruments. Such a construction enables the use of phase shifting devices whereby the accurate adjustment of the phase relation between the interruptor and rectifier may be obtained. This adjustment is necessary in order to obtain perfect synchronism because the mere use' of the same frequency of the current in both the interrupter and the rectifier insures only that these devices will be in step and does not insure their perfect electrical synchronism. Synchronism requires that the devices be operated not only in 'step but also in proper phase relation. In the embodiment as shown, the proper phase relation is maintained by the use of a phase shifter device i'll connected in series with the rectiiier coil ifi.

The operation is as follows:

At the beginning of the time interval during which the measurement is to be made, the condenser i, which at that moment exhibits a voltage of a certain magnitude, is charged'by the current from the battery 2, the switch fi being in the leithand position so as to close the circuit through the battery, the condenser, and the resistance 3. The beginning of said time interval may be determined, for instance, by a sound impulse, and

the end of said time interval is then determined by the arrival of -the echo of said sound impulse. At the end of said time interval, the condenser i has acquired, by the charging operation referred to above, a voltage V2 diierent from its'original voltage V1. It is well-known that if a constant charging voltage is applied rto a condenser (as in the instant case), the difference between the two voltages V1 and V2 will be a function of the time during which the charging operation continues; i

thus, if the two limit values V1 and V2 are known or ascertained, there can be determined from them the time interval duringwhich such change of voltage has taken place. Upon the arrival of the echo (that is, at the end of the time interval during which the measurement is to be made), the switch i is thrown to the right-hand position shown in Fig. 1, so that the condenser i will be in circuit with the grid of the tube 5. This circuit will be opened and closed periodically by the armature of the mechanical interruptor, the said armature being caused to vibrate by the interaction of the magnet I7 with the armature c'oil Q which receives current from the alternating current. source it, so that the armature vibrates in accordance with the frequency of suchl current. The continuous and practically constant direct current supplied by thecondenser iisthus broken up into discontinuous' fragments or current impulses, which together constitute a variable current. 'Ihese impulses are conducted to the grid of the tube 5, where they are amplified. The anode current of said tube passes by way of the condenser I8 to the primary of the transformer Il, andv since this anode current is a variable current, it induces another current in the secondary-of said transformer, which secondary current (of alternating character), is conducted to the mechanical interruptor or rectifier Il. The vibrating armature I2 of this rectifier vcarries a coil I3 in circuit with the secondary oi ,other interrupter.

aisance the transformer ill. The rectified current is conducted to the direct-current measuring instrument l5, a variable resistance iti being arranged in a shunt to said instrument. The voltage indicated by said instrument is e, measure of the time interval to be measured.

The two'h mechanical interrupters operate in perfect synchronism, the particular' frequency ci? their vibrations being immaterial, as long as it is the same foreach of the interrupters, and provided also the two interrupters agree in phase, that is to say, the phase of one interrupter should not exhibit any shift relatively to the phase of the In order that this coincidence of phase may be established, i have provided the adjustable phase shifter il', ci? any well-known or y approved type, by means of which. I am enabled to eliminate, or compensate for, any phase diiference or shift that may happen to exist between the mechanical interrupter il, ti, ii and the ine-y chanical rectifier i2, ifi, Ht.

As above stated the novel connection has the advantage that the functioning of the microchronometer is independent of the characteristic of the tube employed and that a tube may, consequently, be easily replaced by another. In this case, it is suiicient to adjust the connection only as to a measuring value by correspondingly adjusting the shunt resistance it, i. e., at a predetermined value of the condenser voltage l, to cause by adjusting the resistance i6 the pointer of the measuring instrument i5 to move over the scale until the corresponding voltage value is attained. Y

The novel microchronometer is particularly employed in connection with echo depth sounders. in this connection it is desirable to continuously determine the height or depth to be measured and to continuously indicate the same.

In order to attain this it is advisable, as proposed in German Patent 589,368, to use several condensers instead of one. In Fig. 1 is -shown only in a diagrammatic form the manner in which the condenser l may be charged and connected to the grid of the amplifying tubeS by throwing over the switch t. When using a plurality of condensers the change-over or switching of the several condensers, i. e., the cyclic `alternation of the functions thereof, may be eected periodically, approximately at intervals of 2 seconds, so that during 2 seconds one condenser is used for measuring and the second for indicating etc.

li claim as my invention:

1. Arrangement for measuring a source of di.

^ uctuations, rectifying means connected into the outputv side of said amplifier and means for operating said rectifying means in electrical synchronism with said converting means for reconverting the uctuating ampliiled current into continuous direct current, and a direct current measuring instrument connected `with said rectifying means for indicating the magnitude of the resulting direct current as a measure for the voltage of said direct current potential source.

2. Arrangement for measuring a source oi direct current potential, comprising means for converting the D. C. voltage into a uniformly uctu'- ating ,voltage of corresponding value, a. thermionic tube amplifier having its grid connected to said converting means for amplifying said volt-A age fluctuations, rectifying means connected into the output side o! said amplifier and operating synchronously with said converting means for reconverting the fluctuating amplified current into continuous direct current, and a direct current measuring instrument connected with said rectifying means for indicating the magnitude of the resulting direct current as a measure for the voltage o said direct current potential source, and a variable resistance connected in shunt with said direct current measuring instrument, for calibrating the measure of the indications of the latter in accordance with the amplifying characteristics of said tube amplier.

3. Arrangement for measuring a source of direct current potential, comprising means for converting the D. C. voltage into a uniformly uctuat-- ing voltage of corresponding value, a thermlonic tube amplier having its grid connected to said converting means for amplifying said voltage fluctuations. a transformer connected with its primary winding into the output circuit of said amplier, rectifying means connected in circuit with the secondary transformer winding and means for operating said rectifying means in electrical synchronism with said direct current voltage converting means for reconverting the fiuctuating -amplied current into continuous direct current, and a direct current measuring instrument connected with said rectifying means for indicating the magnitude ot the resulting direct current as a measure for the voltage of said direct current potential source.

HANS SCHUCHMANN. 

